Hi!It’s my first time to write my question to you with this method. I don’t know if the method is right. And if there is any trouble with you, I am sorry.My problem is about a force of two group. In simple terms, my model is that the middle layer of polymer chains is pressed with two fcc cryatal. What I need to calculate is the pressure between layer and the upper crystal. The units id LJ,and the command is compute group/group. And I found the force is equal with different size of model in a same load(the load way via the command of “addforce”). In other words, The force output by thermo_style with ADDFORCE command at the same load should increase proportionally. However ,the result is identical.And then I read the manual of units and group/group command!The manual say that force in three direction are “extensive”, and extensive quantities are output by SUM/ATOM. What? This is contrary to the group/group command/In the next I tested the easy model with different size. And I got the same conclusion.And can you tell me where I have wrong?The following is my in.test.units ljatom_style bonddimension 3boundary p p sspecial_bonds fene